The polyphenylene ether resins and methods for their preparation are known, and moreover, described in the patent literature, including U.S. Pat. Nos. 3,306,874 and 3,306,875 (Hay) and U.S. Pat. Nos. 3,257,357 and 3,257,358 (Stamatoff). The polyphenylene ether resins are also known to be combinable with other polymers to form compositions which are extrudable and moldable into products characterized by outstanding properties. Cizek, in U.S. Pat. No. 3,383,435 describes blends of polyphenylene ether resin and polystyrene. Lee, Jr. in U.S. Pat. Nos. 4,166,055 and 4,239,673 discloses blends of polyphenylene ether, polyolefin and styrene-butadiene block copolymer.
Haaf and Cooper, in U.S. Pat. No. 4,172,826, describe flame retardant thermoplastic compositions of a polyphenylene ether resin, a block copolymer and a styrene resin which have been modified by adding an EPDM rubber (that is, a rubbery terpolymer of ethylene, propylene and a diene monomer). As shown in examples of the patent, the EPDM rubber is present in amounts equivalent to or less than the polyphenylene ether resin, and it functions primarily to confer better impact resistance in the polyphenylene ether resin.
The emphasis in many of these patents is on improving the properties of the polyphenylene ether resins and blends by modifying them with other polymers. The polyolefins, and particularly rubbery olefinic polymers, themselves constitute an important family of industrial materials, however. For instance, olefinic rubbers are now employed in formulations for insulation material in electrical wires and cables, and such material is characterized by good elastic properties, but in the typical case lacks good flame resistance in the absence of special additives.